Electrostatic-mediated intramolecular cross-linking polymers in concentrated solutions

Abstract

Since Kuhn in 1956 first proposed intramolecular cross-linking of isolated single-polymer chains in dilute solutions, the method has been extensively employed to achieve single-chain colloids and tadpole colloids (Janus ones) from homopolymers and copolymers, respectively. After understanding that the conventional fabrication methods were based only on short-ranged protections, it has become an urgent requirement to develop new conceptual general methods toward the intramolecular cross-linking in concentrated solutions to determine the improvement of stability. Thus we immediately proposed that if long-ranged, electrostatic-mediated intramolecular cross-linking of polymers could be achieved in concentrated solutions, it would benefit the establishment of more stable supermicelle aggregates. We thought it wise to employ previously developed electrostatic repulsion technique via modificationwith monovalence agents and performed sequential cross-linking with multiple-valence agents. For the fabrication of polyvinylpyridine-contained polymers, iodoethane and 1,5-diiodopentane were used as a modification agent and a cross-linker. For the polyacrylic-acid-contained polymers, 1-methylimidazole and 1,6-hexanediisothiocyanate were used for the intramolecular cross-linking. Polyisoprenecontained polymers were chosen because they were cheap. After click reaction with mercaptoacetic acid, the fabricated polymers resembled polyacrylic-acidcontained polymers. Intramolecular cross-linking of polystyrene-block-poly(4-vinylpyridine)-block-poly (ethylene oxide) (PS-b-P4VP-b-PEO) was achieved at 300 mg/mL. We found that the composition and performance of the colloidal domains were broadly tunable by favorable growth of functional materials, unveiling new perspectives for deriving a huge family of functional composite Janus colloidal single chains.